Advocates of legalization have crafted a plan that could alienate businesses and key Republicans, including Sen. John McCain. But it is designed to lure a powerful new ally -- organized labor.

WASHINGTON — With their prospects in Congress sinking along with the economy, liberal advocates of giving undocumented immigrants a path to citizenship are launching a risky strategy to push lawmakers and the White House to take up their cause.

They are devising a proposal in which millions of undocumented workers would be legalized now, while the number of foreign workers allowed to enter the country would be examined by a new independent commission, and probably reduced.

It is a calculation designed to win a new and powerful ally, organized labor, which favors a limit on foreign worker visas. But it risks alienating businesses that rely on temporary workers and could turn off key Republicans such as Sen. John McCain of Arizona, who in the past has crafted his own compromise plan for legalization.

With unemployment on the rise, the immigration debate has moved to the back burner as lawmakers fear enacting a law that could be portrayed as beneficial for immigrants at the expense of struggling American workers.

Advocates believe that winning support from the AFL-CIO, which opposed previous legalization plans, will help get the issue back on track.

"Last time the coalition was not quite as solid as we would have hoped," said Ali Noorani, director of the National Immigration Forum, one of the advocacy groups negotiating with labor leaders over the new strategy.

Ana Avendano, the AFL-CIO's point person on the issue, said the labor federation believes the Democrats' enhanced power in Washington represents a "sea change" in which liberal groups can forge ahead without working with Republican-leaning business lobbyists.

"The reality is that we no longer have corporations controlling public policy in the White House and on the Hill," she said.

President Obama reiterated his support for legalization last week during a stop in Southern California, and he told members of the Congressional Hispanic Caucus that he would deliver a public statement of support this spring. But advocates are growing anxious that he might prefer to delay what would no doubt be a politically charged fight. Immigration advocates have already raised concerns that the administration has not called off workplace raids that are splitting immigrant families.

Rep. Luis V. Gutierrez (D-Ill.) said he and other caucus members leaned on the president to act fast, pointing out that he had found time to satisfy other constituencies.

"We're saying, 'OK, you took time out for stem cell research, and you're taking time out for healthcare,' " Gutierrez said. "And our communities expect you to take time out for our issues."

To bolster their cause, advocates are planning an $18-million media and grass-roots campaign for the fall. The funding is coming primarily from liberal foundations, including one founded by billionaire activist George Soros.

Any new legalization plan is likely to look similar in some respects to the bill crafted by McCain and Sen. Edward M. Kennedy (D-Mass.), which stalled most recently in 2007. Opponents had decried the measure as "amnesty," but it would have required undocumented workers to pay a fine and back taxes and to wait longer than other applicants for permanent residency status.

The new proposal, as laid out by several participants in the behind-the-scenes negotiations, would also create an independent commission that would assess labor and industry data to decide how many foreign workers should be allowed into the country. The system, designed by Ray Marshall, a Labor secretary under President Carter, would replace a maze of special temporary worker visas that are granted each year to high-tech specialists, agriculture workers and other foreigners brought into the U.S. by foreign and domestic firms.

Advocates said they planned to remind House members and senators that Latino voters, who supported Democrats in big numbers in the 2006 and 2008 elections and proved crucial to Obama's victories in Florida and the Southwest, are expecting the party to use its enhanced power to pass a legalization plan.

Some close to the White House said in interviews that the administration might prefer to wait until 2011 to advance an immigration bill. But one Democrat who supports more immediate action is Senate Majority Leader Harry Reid, who is facing a tough reelection battle next year in Nevada, where Latinos make up a growing share of voters.

A spokesman for Reid said Thursday that the senator planned for the immigration debate to occur this fall but did not say whether he would back the efforts to court labor leaders.

Officials at the U.S. Chamber of Commerce said Thursday that a solidly Democratic coalition pushing for immigration changes would prove far less effective in the end. Passage in the Senate requires 60 votes to head off a filibuster, and several conservative Democrats are likely to oppose the measure. That means the bill needs GOP support.

"If they want to go on their own and get 60 votes, good luck," said Angelo Amador, director of immigration policy at the chamber. He added that business lobbyists recognized the heightened power of unions and Democrats, and "we'll be willing to accept some additional union protections. But that doesn't mean that the business community is going to roll over and play dead."